It is well known in the prior art to provide an air bag restraint system in a vehicle. The air bag restraint system typically includes an inflator and an air bag for inflation upon discharge of gas by the inflator. It is known that the air bag restraint system may be mounted beneath an opening in an instrument panel through which the air bag deploys for protection of a vehicle passenger. Preferably, the instrument panel opening is normally closed by a cover door which is forced opened by the deploying air bag. The cover door covers the air bag restraint system during normal operation of the vehicle and may also be used to guide the air bag during deployment.
It is known in the prior art that the cover door may be connected to the vehicle, such as by connection to the instrument panel or to the air bag restraint system, by a tether which is attached to the cover door. The tether typically includes a main body portion which is attached to the cover door and end portions which extend out beyond the cover door and to the vehicle for anchoring the cover door. The connection of the tether to the cover door must be strong enough to withstand the forces of the opening cover door during air bag deployment. A conventional process for connecting the tether to the cover door includes providing a molded plastic cover substrate. A separate tether is cut to shape and laid over the cover substrate. The cover substrate may include a slot on each end through which respective end portions of the tether are fed. The tether is smoothed over the cover substrate as much as possible and then the tether is ultrasonically welded or heat staked to the cover substrate at numerous locations, for example such as eighteen for a single cover. Any openings in the cover substrates, such as those through which the tether ends extends or through which any other clips or brackets may need to extend, must be manually taped closed to avoid foam bleed-through in the next step of the process. Finally, the foam is molded over the tether on the cover substrate with a thin outer layer of thermoplastic or vinyl skin placed over the foam. Alternately, the tether may be laminated on the cover door between the cover substrate and an outer foam layer.
To better withstand the forces of the opening cover door during air bag deployment, the tether is preferably located on top of the cover substrate directly beneath the show surface of skin and foam. One difficulty in the prior art arrangement is that loose portions of the tether which are not staked to the cover substrate may bend or shift during the foaming process and been seen from the show surface. Thus, it will be appreciated that the taping, welding or heat staking, lamination, or movement of the tether itself may cause an uneven show surface in the final cover door when the foam and skin are placed over the cover substrate and tether. In addition, there is a concern with bleed-through of the foam at the slots through which the end portions of the tether extend and which are manually taped over in preparation for the foam and skin. Also, the prior art requires that the main body portion of the tether cover a substantially large portion of the cover door and that numerous attachment locations be provided to secure attachment of the tether to the cover substrate. In addition, the tether in the prior art is placed between the substrate and the outer foam layer and is not integrally connected to the cover substrate.